Listeria!! MICROM 442 Deck 12

Question 1

Listeria monocytogenes short and GM?

Answer 1

positive rods or cocobacilli

Question 2

catalase?

Answer 2

+

Question 3

appearance on blood agar

Answer 3

beta-hemolytic on blood agar; grows at low
[refrigerator] temperatures, low pH, high salt

Question 4

internalins InlA and InlB allow binding to and invasion of
non-phagocytic cells

Answer 4

• InlA binds E-cadherin on intestinal epithelial cells
• InlB binds HGFR [hepatocyte growth factor receptor]
• involved in crossing critical anatomical membranes

Question 5

Listeriolysin O [LLO]

Answer 5

• cholesterol-dependent pore-forming cytolysin
• Listeria unable to replicate in phagosome;
• grows well in cytosol
• LLO causes lysis of bacteria-containing phagosome
• LLO-mutant is avirulent
• lytic activity limited by pH optima, translational
  regulation and proteolytic degradation by
  proteasome

Question 6

release bacteria from phagosome

Answer 6

Phospholipases

Question 7

ActA: surface protein with polar distribution is key for cell-to-cell spread

Answer 7

• promotes actin polymerization: so-called “comet tails”
  that push bacteria through cytoplasm
• plasma membrane of neighboring cell pinches off
  forming double-membrane compartment
• LLO/phospholipases allow release into cytosol

Question 8

Immunity depends upon what type of cell?

Answer 8

CD8+ T cells

Question 9

Frequently food-born

Answer 9

incubation period longer than
most other food-born illnesses; outcome depends upon
host attributes

Question 10

Pregnant women and their fetuses

Answer 10

• Vertical transmission: feto-placental infections
• early onset: septicemia in utero
• late onset: exposure during birth;
• meningitis 2-3 wks later

Question 11

Elderly; alcoholism; diabetes; corticosteroid use;
individuals with compromised cellular immunity

Answer 11

• Meningitis [presents similar to other CNS bacterial
  infections: fever, headache, stiff neck]
• Septicemia

Question 12

Immune competent hosts: gastrointestinal infections

Answer 12

• mild flu-like symptoms [low inoculum]
• febrile gastrointestinal infections [high inoculum]

Question 13

Dx:

Answer 13

Cx CSF, blood, amniotic fluid, placenta, fetal tissue;
tumbling motility at RT [non-motile at 37C]